1. Technical Field
The present invention relates to a post-processing apparatus that performs various post-processing operations on a center-folded booklet, and an image forming system including the post-processing apparatus.
2. Description of Related Arts
In recent years, post-processing apparatuses for performing various post-processing operations on a printed sheet output from an image forming apparatus, such as a printer or an MFP, have been increasing used. The term “post-processing operations” refers to, for example, an operation of center-folding a sheet (“folding operation”), an operation of binding a plurality of sheets with a staple (“stapling operation”), an operation of cutting an edge of a booklet (“cutting operation”), and an operation of forming a spine of a booklet (“square folding operation”), and the like.
Referring to FIG. 9A, when performing a cutting operation on a center-folded booklet B, it is necessary to clamp the booklet B with clamps 371 and 372. In the process of transferring the booklet B to the clamps 371 and 372, the position of a fold F may become displaced from the central position in the booklet B in the thickness direction.
If a cutting operation is performed on the booklet B, which is clamped in a state in which the fold F has been displaced, a cut edge E of the booklet B becomes inclined with respect to the thickness direction, so that the appearance of the finished booklet B is not good (see FIG. 9B). Likewise, referring to FIGS. 10A and 10B, if a square folding operation is performed on the booklet B, which is clamped in a state in which the fold F has been displaced (FIG. 10A), the position of a staple S may become displaced from the central position in the thickness direction or the cut edge E may become inclined, so that, also in this case, the appearance of the finished booklet B is not good (FIG. 10B). In the present example, the square folding operation is performed by moving a roller R back and forth in directions perpendicular to the plane of FIGS. 10A and 10B.
Regarding this problem, Japanese Unexamined Publication Nos. 2007-118518, 2010-195582, and 2010-241112 describe post-processing apparatuses that clamp a booklet with clamp members after pressing an end of the booklet against contact members of various types. However, even with such post-processing apparatuses, if the booklet is too strongly pressed against the contact member, the end of the booklet may become deformed, so that it is difficult to appropriately correct displacement of a fold. Japanese Unexamined Publication No. 2005-040890 describes a post-processing apparatus that clamps a portion of a booklet near an edge with clamp members. The post-processing apparatus can perform a cutting operation with high precision, but cannot correct displacement of a fold.
The present invention has been achieved to address the problems of existing technologies described above. One of the objects of the present invention is to provide a post-processing apparatus that can correct displacement of a fold in the thickness direction of a booklet that is clamped by clamped members for various post-processing operations, and an image forming system including the post-processing apparatus.